Mysql数据库多行记录的某一字段，根据分组合并group_concat

mysql多行记录的某一字段，根据分组进行合并，合并的数据用逗号分隔开

使用以下SQL语句的执行结果

SELECT
 school_id,
 grade,
 sex,
 group_concat(physical_item) as physical_item
FROM
 phy_examination_items
GROUP BY
 school_id,
 grade,
 sex